Field of the Invention
The present invention relates to a focus detecting unit configured to provide a focus detection based on a signal from an image sensor.
Description of the Related Art
Japanese Patent Laid-Open No. (“JP”) 2013-140380 discloses an image pickup apparatus having an image sensor that serves as a focus detecting element. The image pickup apparatus disclosed in JP 2013-140380 discloses a method of storing, when the half-mirror is inserted into the optical path, an image-plane moving amount caused by the insertion of the half-mirror, as an offset amount of a defocus amount by considering the F-number in the image pickup lens, and of correcting the defocus amount.
However, the image pickup apparatus disclosed in JP 2013-140380 does not consider a positional shift of a pupil corresponding to each focus detecting pixel caused by the insertion of the half-mirror, or in turn a change of shading.